This invention relates to novel semi-flexible foams that have good heat insulating properties, are flame-retardant and light in weight, and to the process for producing said foam.
Conventional heat-insulating foams are made of polyurethane, polyisocanurate or combinations thereof such as disclosed in U.S. Pat. Nos. 3,931,065 and 4,184,022 in an attempt to produce an inexpensive insulation having high heat insulating properties, stability and fire retardance. However, known products are typically dense and heavy, expensive to produce, friable, have poor fire retardance, or lack stability and have poor resistance to changes in weather conditions.
Polyurethane foams, for example, burn readily when ignited and flame retardant chemicals are normally added in an effort to retard combustion by rendering the foam self-extinguishing, intumescent, or capable of producing a char. U.S. Pat. No. 4,514,524 discloses a polyurethane foam having a halogenated flame retardant and water or alcohol soluble urea-formaldehyde resin added thereto in an attempt to overcome the natural propensity of polyurethane to burn by improving flame retardancy and by adding intumescent properties.
Polyisocyanurate foams can be given high-temperature resistance but they normally remain very brittle and accordingly are subject to damage when handled. Canadian Patent No. 1044847 discloses a typical isocyanurate foam adapted for a high temperature application.
Urea foams have high temperature thermal stability but are very fragile and friable and accordingly generally are considered not suitable as an insulating material.